diff --git a/glfw/upstream/glfw/src/x11_window.c b/glfw/upstream/glfw/src/x11_window.c
index 5fdf7819..85d2da44 100644
--- a/glfw/upstream/glfw/src/x11_window.c
+++ b/glfw/upstream/glfw/src/x11_window.c
@@ -2123,8 +2123,8 @@ void _glfwPlatformSetWindowIcon(_GLFWwindow* window,
         for (i = 0;  i < count;  i++)
             longCount += 2 + images[i].width * images[i].height;
 
-        long* icon = calloc(longCount, sizeof(long));
-        long* target = icon;
+        unsigned long* icon = calloc(longCount, sizeof(unsigned long));
+        unsigned long* target = icon;
 
         for (i = 0;  i < count;  i++)
         {
@@ -2133,10 +2133,10 @@ void _glfwPlatformSetWindowIcon(_GLFWwindow* window,
 
             for (j = 0;  j < images[i].width * images[i].height;  j++)
             {
-                *target++ = (((long)images[i].pixels[j * 4 + 0]) << 16) |
-                            (((long)images[i].pixels[j * 4 + 1]) <<  8) |
-                            (((long)images[i].pixels[j * 4 + 2]) <<  0) |
-                            (((long)images[i].pixels[j * 4 + 3]) << 24);
+                *target++ = (((unsigned long)images[i].pixels[j * 4 + 0]) << 16) |
+                            (((unsigned long)images[i].pixels[j * 4 + 1]) <<  8) |
+                            (((unsigned long)images[i].pixels[j * 4 + 2]) <<  0) |
+                            (((unsigned long)images[i].pixels[j * 4 + 3]) << 24);
             }
         }